WASHINGTON (Reuters) – U.S. lawmakers unleashed a barrage of criticism on Veterans Affairs Secretary Eric Shinseki on Thursday, saying his muted response to a growing scandal over deadly health care delays for veterans was not good enough.

At a hearing before the Senate Veterans Affairs Committee, senior Democrats joined Republicans in demanding stronger action to fix problems after officials at VA medical facilities in Phoenix were accused of covering up long wait times for patients, including 40 who died while awaiting care.

“The standard practice at the VA seems to be to hide the truth in order to look good. That has got to change once and for all,” Democratic Senator Patty Murray told Shinseki.

Senator Richard Blumenthal, another Democrat, said there was “solid evidence of wrongdoing within the VA system,” and added that perhaps the FBI should be brought into the probe.

Shinseki told the lawmakers that he was “mad as hell” about allegations of schemes to mask waiting times for care at VA facilities, but repeatedly said that VA would wait for its inspector general to complete its investigation before acting on the Phoenix allegations.

The VA has put three senior officials in Phoenix on administrative leave after doctors there said they were ordered to hold veterans’ names for months on a secret waiting list until a spot opened up on an official list that met the agency’s two-week waiting time goals.

“Whatever comes out of this, whatever is substantiated, we will take action,” Shinseki said after the hearing. He said that a nationwide audit of appointment and scheduling practices at all VA hospitals and clinics would deal with the problems.

In a sign the White House is growing concerned about the political fallout from the VA controversy, President Barack Obama on Wednesday directed a top aide, White House deputy chief of staff Rob Nabors, to lead a review of the problems at the VA.

As Shinseki appeared on Capitol Hill, lawmakers expressed growing frustration with the performance of the retired four-star general.

“After Secretary Shinseki’s out-of-touch performance today, it’s no wonder President Obama felt compelled to assign someone from the White House to help clean up the mess at the department,” said Representative Jeff Miller, a Republican who chairs the House Veterans Affairs committee.

Miller added that he did not believe the VA audit would yield useful or accurate results.

Allegations have been reported about similar cover-up schemes at VA medical facilities in at least seven other cities. The agency runs the largest U.S. healthcare group, overseeing some 1,700 hospitals, clinics, nursing homes and other facilities.

Asked if “cooking the books” was a widespread practice, Shinseki said: “I’m not aware, other than a number of isolated cases, where there is evidence of that.”

Veterans’ advocates said they will insist on results.

“We want a proactive secretary, not a reactive one,” Tom Tarantino, policy director for the Iraq and Afghanistan Veterans of America, told senators.